Mobility control in a miscible-type crude oil recover process

ABSTRACT

Improved oil recovery is obtained wherein highly saline water is used in an aqueous mobility buffer by incorporating about 0.05 percent to about 10 percent by weight of a water soluble surfactant in at least the front portion of the buffer, the portion of the mobility buffer equal to at least about 25 percent of the volume of a previously injected micellar dispersion. The mobility buffer is useful in secondary and tertiary oil recovery processes to displace a micellar dispersion through an oilbearing subterranean formation toward a production means to recover oil therefrom. The mobility buffer has a sufficiently low mobility to protect against fingering in the process.

FIP'I' MZE OR" 396589130 United Males ratent 1151 3,658,13

Davis, Jr. et al. [451 Apr. 25, 1972 54] MOBILITY CONTROL IN A MISCIBLE-3,406,754 10/1968 Gogarty ..l66/273 TYPE UDE 01L E VE PROCESS 3,455,3857/1969 Gogarty ....l66/274 3,500,922 3/1970 O'Brien et al ..]66/273Inventors: J Davis, J William J- Kunzmfln, 3,500,924 3/1970 Poettmann..l66/273 x both of Littleton, C010.

73 Assignee: Marathon Oil Company, Findlay, Ohio Attorney-Joseph C.Herring, Richard C. Willson, Jr. and Jack [22] Filed: Aug. 19, 1970 L.Hummel [21] Appl. No.: 65,338 [57] ABSTRACT Related Application DataImproved oil recovery is obtained wherein highly saline water [63]Continuatiomimpart of sen No 762,973 Sept 26 is used in an aqueousmobility bufi'er by incorporating about 1968 abamkmed- 0.05 percent toabout 10 percent by weight of a water soluble surfactant in at least thefront portion of the buffer, the portion of the mobility buffer equal toat least about 25 percent of [52] U.S.Cl ..l66/273 [51] Int. Cl ..E2lb43/22 the {Q prevlotlsly Injected mlcenar dlspefs'on' The 58 Field ofSearch ..166 273-275 305 R mblmy buffer useful secmdary and ternary Emmyprocesses to displace a micellar dispersion through an oil- 56]References Cited bearing subterranean formation toward a productionmeans to recover oil therefrom. The mobility buffer has a sufficientlyUNITED STATES PATENTS low mobility to protect against fingering in theprocess.

3,266,570 8/1966 Gogarty 1 66/273 17 Claims, No Drawings MOBILITYCONTROL IN A MISCIBLE-TYPE CRUDE OIL RECOVER PROCESS CROSS REFERENCE TORELATED APPLICATIONS This is a continuation-impart of our copendingapplication, Ser. No. 762,973, filed Sept. 26, I968, and now abandoned.

Also, U.S. Pat. No. 3,500,924, issued Mar, 17, 1970 teaches the use ofsurfactants in the front portion of the mobility buffer to facilitateemulsification of the back portion of a preceding micellar dispersionslug with the front portion of the mobility buffer slug.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to injecting a micellar dispersion, followed by a mobilitybuffer, into an oil-bearing subterranean formation and displacing thedispersion toward a production well to recover crude oil. A highlysaline water can be used in the mobility buffer by incorporatingsurfactants within the front portion thereof.

2. Description ofthe Prior Art Gogarty et al. teach in U.S. Pat. Nos.3,254,714 and 3,275,075 that micellar dispersions are useful to recovercrude oil from an oil-bearing subterranean formation. A mobility buffer,having a sufficiently low mobility to impart viscous stability to theprocess, is useful with these processes to obtain a more efficient oilrecovery. The mobility buffer is generally an aqueous medium containinga mobility reducing agent-the amount of agent being sufficient to impartthe desired mobility to the process. Examples of mobility agents includepartially hydrolyzed high molecular weight polyacrylamides,polysaccharides, and any agent which effectively reduces the mobility ofwater flowing through a porous medium.

The water used in the mobility buffer is of prime importance. If ahighly saline water is used, more of the mobility reducing agent isgenerally needed to obtain the desired mobility. Also, the oil recoveryefficiency is generally adversely affected. Thus, if the process isbeing effected in a territory where available water is of a high saltcontent, the water will desirably have to be diluted with fresh water inorder to obtain an economical and efficient flood.

Applicants have discovered that by incorporating water solublesurfactants in at least the front portion of the mobility buffer, ahighly saline water solution can be used as a majority of the fluid inthe mobility buffer. The overall effect is to obtain a more efficientflooding process while using highly saline water in the mobility buffer.

DESCRIPTION OF THE INVENTION The term micellar dispersion as used hereinis meant to include micellar solutions, microemulsions, transparent"emulsions, etc. Specific examples of useful micellar solutions includethose taught in U.S. Pat. Nos. 3,254,714 and 3,275,075 to Gogarty etal.; 3,307,628 to Sena; 3,356,138 to Davis et al.; 3,506,070 to Jonesand 3,497,006 to Jones et al.

The micellar dispersions of this invention can be either oilexternal orwater-external, but are preferably oil-external. They containhydrocarbon, aqueous medium, surfactant sufficient to impart micellarcharacteristics to the dispersion, and optionally consurfactant(s)and/or electrolyte(s). Examples of volume amounts include about 4percent to about 60 percent or more, of hydrocarbon, about percent toabout 90 percent aqueous medium, at least about 4 percent surfactant,about 0.01 percent to about percent of cosurfactant, and about 0.001percent to about 5 percent or more by weight (based on the aqueousmedium) of electrolyte. A high water content is generally desired toimprove process economics.

Examples of hydrocarbon include crude oil, partially refined fractionsof crude oil, and refined fractions thereof. Specific examples includeside cuts from crude oil columns, lubricating oils, mineral oil, gasoils, crude column overheads, kerosene, gasoline, naphthas, andliquefied petroleum gases.

The aqueous medium used to make-up the dispersion can be soft, brackish,or brine water. Preferably, the water is soft, but it can contain smallamounts of salts which are preferably compatible with the formationfluids. In some instances, it is desired the aqueous medium containlarge amounts of salts characteristic of the salts within thesubterranean formation.

The surfactant can be nonionic, cationic, or anionic. Specific examplesof useful surfactants can be found in U.S. Pat. No. 3,275,075 to Gogartyet al. Preferably, the surfactant is a petroleum sulfonate, also knownas alkyl aryl naphthenic sulfonate, and preferably contains a monovalentcation. Ex amples of preferred surfactants are sodium and ammoniumpetroleum sulfonates having an average equivalent weight within therange of about 350 to about 520 and more preferably about 390 to about470. The sulfonate molecule can have more than one sulfonate grouping.The sulfonate can be a mixture of any two or more low, medium, and highaverage equivalent weight sulfonates or a mixture of two or moredifferent surfactants.

The cosurfactants, also identified as cosolubilizers and semi-polarorganic compounds, can be alcohols amino compounds, esters, aldehydes,ketones, and like materials containing from one to about 20 or morecarbon atoms. More preferably, the cosurfactant contains about three toabout 16 carbon atoms and is preferably an alcohol. Examples of usefulalcohols include isopropanol, nand isobutanol, amyl alcohols such asn-amyl alcohol, land Z-hexanol, land Z-octanol, decyl alcohols, alkarylalcohols such as p-nonyl phenol, alcohols containing two or more hydroxygroupings and can optionally contain an ether group(s) etc. within thealcohol, and alcoholic liquors such as fusel oil. Preferably, theconcentration can be within the range of about 0.1 percent to about 5percent. Mixtures of two or more cosurfactants are also useful.

The electrolytes include inorganic bases, inorganic acids, inorganicsalts, organic bases, organic acids, and organic salts which arestrongly or weakly ionized. The inorganic bases, acids, and salts arepreferred, specific examples include sodium hydroxide, sodium chloride,sodium sulfate, hydrochloric acid, sulfuric acid, and sodium nitrate.Additional examples of useful electrolytes can be found in U.S. Pat. No.3,330,343 to Tosch et al. The electrolyte can be the salts withinbrackish or brine water.

The micellar dispersion is first injected into the oil-bearingsubterranean formation. This is followed by a mobility buffer, onepurpose being to impart a favorable mobility to the flooding process.For example, the mobility buffer protects the micellar dispersion frominvasion by the drive water which follows the mobility buffer. Bymaintaining a favorable mobility condition throughout the process, ormost of the flooding process, a more efficient and effective floodingoperation can be obtained.

The mobility buffer is composed of an aqueous medium and a mobilityreducing agent. The purpose of the mobility reducing agent is to impartto the mobility buffer a sufficiently low mobility to protect againstfingering. The aqueous medium in the mobility buffer is desirably acheap one or one that is locally available. This invention teaches thathighly saline solutions can be used as the aqueous medium within themobility buffer by incorporating water soluble surfactants within themobility buffer. Examples of saline solutions include concentrations upto and above 100,000 ppm of dissolved salts. The mobility reducing agentcan be any chemical soluble in the water which imparts a lower mobilityand is compatible in the overall flooding process. Specific examplesinclude polysaccharides, partially hydrolyzed, high molecular weightpolyacrylamides, e.g. those marketed under the trade name of Pusher, atrademark of Dow Chemical Company, Midland, Michigan; in general, watersoluble polyelectrolytes having molecular weights in excess of 500,000,etc. Oil/water emulsions are not intended to be within the definition ofmobility buffer as used herein.

The surfactants useful in the mobility buffer include any water-solublesurfactant. The surfactants can be anionic, nonionic, cationic, oramphoteric. Specific examples include those water-soluble surfactantspreviously identified as surfactants useful in the micellar dispersion:Santomerse 85, a dodecyl benzene sodium sulfonate, manufactured byMonsanto Chemical Company; Duponol ME 939, technical grade sodium laurylsulfate, manufactured by E. l. DuPont deNemours & Company; GantrezAN-ll9, a poly(methyl vinyl ether/maleic anhydride) manufactured byGeneral Aniline & Film Corporation, Dyestuff 8!. Chemical Division; Brij78 4-156, a polyoxyethylene stcaryl ether, manufactured by AtlasChemical Industries; Duponol WA 428, technical grade sodium laurylsulfate, manufactured by E. I. DuPont deNemours & Company; and Duponol G871, a fatty alcohol amine sulfate manufactured by E. l. DuPontdeNemours & Company. Also included are alkyl and aryl, and substitutedalkyl and aryl sulfates, carbonates, nitrates, amides and otherwater-soluble salts; hydrocarbon sulfonates, e.g. petroleum sulfonate,having an average equivalent weight within the range of about 150 toabout 400 and more preferably about 200 to about 350 (the unneutralizedsulfonic acids obtained in manufacturing petroleum sulfonates are alsouseful and are meant to be included within the term sulfonates);polyoxyethylene alkylethers, condensates of ethylene oxide with analkyloxide (e.g. propylene oxide), and an alkyl hydroxide (e.g.propylene glycol); ethylene diamine tetracetic acid; and like materials.Preferably, the surfactant is compatible with the other components usedin the process and with the connate fluids. In addition, the surfactantis desirably chosen such that it will not be readily adsorbed on thereservoir rock. Amounts within the range of about 0.05 percent to about10 percent, and more preferably from about 0.2 percent to about 5percent, based on the aqueous medium within the mobility buffer, impartdesired characteristics to the process.

The volume of the mobility buffer that contains the surfactant can varyfrom that volume equal to about 25 percent to percent of the micellardispersion volume previously injected to at least a majority of themobility buffer volume. Preferably, that volume equal to about 50percent of the micellar dispersion volume to less than 50 percent ofmobility buffer volume and, most preferably, about 50 percent to about100 percent ofthe micellar dispersion volume contains surfaclam.

The following example specifically illustrates working embodiments ofthe invention. This example is not to be interpreted as limiting theinvention. Rather, equivalents obvious to those skilled in the art areintended to be equated within the scope of the invention as defined bythe specification and appended claims. Unless otherwise specified, allpercents are based on volume.

EXAMPLE Berea sandstone cores, 4 feet by 2 inches in diameter, areflooded with percent pore volume ofa micellar dispersion of 55.0 percentcrude column overhead, l0.4 percent of an ammonium petroleum sulfonatehaving an average equivalent weight of about 420-440 and being about 62percent active, 31.9 percent of an aqueous medium containing about10,200 ppm of dissolved solids (salts), and about l.85 percent ofalcohols (1.7 percent isopropyl alcohol and 0.15 percent nonyl phenol).The micellar dispersions are followed l.2 pore volumes of a mobilitybuffer, the composition of the mobility buffer being defined withinTable l. The mobility reducing agent is DOW 500 Series Pusher, apartially hydrolyzed high molecular weight polyacrylamide marketed byDow Chemical Company, Midland, Michigan. Half of the runs do not containa surfactant within the mobility buffer whereas the other half docontain surfactant. The surfactant is Gafen FA-5, a trademark of GeneralAniline & Film Corporation, identified as a dialkyl phenoxypoly(ethyleneoxy) ethanol. The Berea sandstone cores are first saturatedwith an aqueous medium containing about 20,000 ppm. total dissolvedsolids, flooded with crude oil (obtained from the Henry lease, Robinsonsand, Crawford County, Illinois), and then flooded with an aqueousmedium containing about 20,000 ppm of dissolved solids to residual oilsaturation. The results of the tests are indicated in Table I:

The above data indicate, especially at the 50,000 and 100,000 ppm levelof NaCl in the mobility buffer, that the incorporation of surfactantwithin the mobility buffer improves the oil recovery. Thus, highlysaline water can be used efficiently in the mobility buffer by theaddition of such surfactants.

What is claimed is:

l. in an improved process of recovering oil from an oil-bearingsubterranean formation wherein a volume of micellar dispersion isinjected into the formation and displaced toward a production means byan aqueous mobility buffer fluid and a water drive to recover crude oilthrough the production means, the improved process step comprisingincorporating into the front volume of the mobility buffer fluid, thefront volume equal to at least about 25 percent of the volume of themicellar dispersion, a water-soluble surfactant to permit the use ofhighly saline water in the mobility buffer fluid.

2. The process of claim 1 wherein the micellar dispersion is comprisedof hydrocarbon, surfactant, and water.

3. The process of claim 2 wherein the micellar dispersion containscosurfactant.

4. The process of claim 2 wherein the micellar dispersion containselectrolyte.

5. The process of claim 1 wherein from about 0.05 percent to about 10percent of water-soluble surfactant is incorporated into the frontvolume of the mobility buffer.

6. The process of claim 1 wherein the mobility buffer contains up to100,000 ppm of salt dissolved in the water.

7. The process of claim 1 wherein the front volume of the mobilitybuffer has a mobility about equal to or less than that of the formationfluids flowing ahead of the micellar solution.

8. The process of claim 1 wherein the front volume of the mobilitybuffer has a mobility about equal to or less than that of the micellardispersion flowing in the formation.

9. The process of claim 1 wherein the front volume of the mobilitybuffer containing the surfactant is equal to about 50 percent to aboutpercent of the volume of the micellar dispersion.

10. in an improved process of flooding an oil-bearing subterraneanformation wherein a volume of a micellar dispersion comprised ofsurfactant, water and hydrocarbon is injected into the formation anddisplaced toward a production means by an aqueous mobility buffer and awater drive to recover crude oil through said production means, theimproved process step comprising incorporating from about 0.05 percentto about l0 percent of a water-soluble surfactant into the front volumeof the mobility buffer, the front volume equal to at least about 50percent of the volume of injected micellar dispersion, to permit the useof highly saline water in the mobility buffer.

11. The process of claim wherein from about 0.2 percent to about 5percent of surfactant is incorporated into the front volume ofthemobility buffer.

12. The process of claim 10 wherein the surfactant in the front volumeofthe mobility buffer is a condensate of ethylene oxide with ahydrophobic condensate of propylene oxide and propylene glycol.

13. The process of claim 10 wherein the surfactant in the front volumeof the mobility buffer is an alkyl phenoxypoly (ethyleneoxy) ethanolcontaining at least one alkyl grouping.

14. The process of claim 10 wherein the surfactant in the front volumeof the mobility buffer is nonionic.

15. The process of claim 10 wherein the surfactant in the front volumeof the mobility buffer is anionic.

16. The process of claim 10 wherein the mobility of the front volume ofthe mobility buffer is about equal to or less than that of the micellardispersion.

17. The process of claim 10 wherein the front volume of the mobilitybuffer containing the surfactant is equal to about 50 to about percentofthe volume ofthe micellar dispersion.

2. The process of claim 1 wherein the micellar dispersion is comprisedof hydrocarbon, surfactant, and water.
 3. The process of claim 2 whereinthe micellar dispersion contains cosurfactant.
 4. The process of claim 2wherein the micellar dispersion contains electrolyte.
 5. The process ofclaim 1 wherein from about 0.05 percent to about 10 percent ofwater-soluble surfactant is incorporated into the front volume of themobility buffer.
 6. The process of claim 1 wherein the mobility buffercontains up to 100,000 ppm of salt dissolved in the water.
 7. Theprocess of claim 1 wherein the front volume of the mobility buffer has amobility about equal to or less than that of the formation fluidsflowing ahead of the micellar solution.
 8. The process of claim 1wherein the front volume of the mobility buffer has a mobility aboutequal to or less than that of the micellar dispersion flowing in theformation.
 9. The process of claim 1 wherein the front volume of themobility buffer containing the surfactant is equal to about 50 percentto about 100 percent of the volume of the micellar dispersion.
 10. In animproved process of flooding an oil-bearing subterranean formationwherein a volume of a micellar dispersion comprised of surfactant, waterand hydrocarbon is injected into the formation and displaced toward aproduction means by an aqueous mobility buffer and a water drive torecover crude oil through said production means, the improved processstep comprising incorporating from about 0.05 percent to about 10percent of a water-soluble surfactant into the front volume of themobility buffer, the front volume equal to at least about 50 percent ofthe volume of injected micellar dispersion, to permit the use of highlysaline water in the mobility buffer.
 11. The process of claim 10 whereinfrom about 0.2 percent to about 5 percent of surfactant is incorporatedinto the front volume of the mobility buffer.
 12. The process of claim10 wherein the surfactant in the front volume of the mobility buffer isa condensate of ethylene oxide with a hydrophobic condensate ofpropylene oxide and propylene glycol.
 13. The process of claim 10wherein the surfactant in the front volume of the mobility buffer is analkyl phenoxypoly (ethyleneoxy) ethanol containing at least one alkylgrouping.
 14. The process of claim 10 wherein the surfactant in thefront volume of the mobility buffer is nonionic.
 15. The process ofclaim 10 wherein the surfactant in the front volume of the mobilitybuffer is anionic.
 16. The process of claim 10 wherein the mobility ofthe front volume of the mobility buffer is about equal to or less thanthat of the micellar dispersion.
 17. The process of claim 10 wherein thefront volume of the mobility buffer containing the surfactant is equalto about 50 to about 100 percent of the volume of the micellardispersion.